The PDF viewer is based on the Mozilla-supported HTML5 project PDF.js, which delivered a JavaScript platform to render PDFs in the browser. The feature was integrated in to the Firefox 19 beta release in January.

Mozilla is promoting easier PDF viewing without the need to install plugins for products like Adobe Reader. It highlighted last month "closed source code" plugins that could potentially expose users to security vulnerabilities.

Mozilla has tackled plugin security issues with its recently broadened Click-to-Play feature, which by default will restrict all browser plugins, except the latest version of Flash, from loading until a user gives it permission.